Signal transmitting and receiving circuit of digital subscriber line

This invention discloses a signal transmitting and receiving circuit of a digital subscriber line used for transmitting an output signal to a telecommunication loop or receiving an input signal from the telecommunication loop. The signal transmitting and receiving circuit comprises a transformer, which is coupled to the telecommunication loop; a signal transmitting module, which is coupled to the transformer, for generating the output signal; a signal receiving module, which is coupled to the transformer, for processing the input signal; an echo cancelling circuit, comprising passive components and having two ends, one of which is coupled to the signal transmitting module and the transformer, the other is coupled to the signal receiving module and the transformer. The output signal is transmitted to the telecommunication loop via the electromagnetic coupling of the transformer, and the input signal is received by the signal receiving module by the electromagnetic coupling of the transformer.